Machines for sharpening cutters



Dec. 3, 1963 R. LlVET MACHINES FOR SHARPENING CUTTERS 7 Sheets-Sheet Filed Jan. 8, 1962 Dec. 3, 1963 R. LlVET MACHINES FOR SHARPENING CUTTERS 7 Sheets-Sheet 2 Filed Jan. 8, 1962 Dec. 3, 1963 R. LIVET 3,112,582

MACHINES FOR SHARPENING CUTTERS Filed Jan. 8, 1962 '7 Sheets-Sheet 55 K Y\ I. I 7 {1 14m 9- x -43 35 m I. 1X

Dec. 3, 1963 R. LlVET 3,112,582

- MACHINES FOR SHARPENING CUTTERS Filed Jan. 8, 1962 '7 Sheets-Sheet 4 Dec. 3, 1963 R. LlVET MACHINES FOR SHARPENING CUTTERS '7 Sheets-Sheet 5 Filed Jan. 8, 1962 Dec. 3, 1963 R. LlVET 3,112,582

MACHINES FOR SHARPENING CUTTERS Filed Jan. 8, 1962 7 Sheets-Sheet 6 Dec. 3, 1963 R. LlVET 3,112,582

MACHINES FOR SHARPENING CUTTERS Filed Jan. 8, 1962 '7 Sheets-Sheet 7 United States Patent 3,112,582 MACHINES FOR SHARPENTNG CUTTERS Roger Livet, 19 Quad Bourbon, Paris, France Filed Jan. 8, 1962, S82. No. 164,656 Claims priority, application France .ian. 13, 1961 9 Claims. (Cl. 51123) My invention has for its object improvements in the cylindrical or conical sharpening of cutters having straight or helical teeth with a predetermined backing off angle.

The main difliculty of such a sharpening resides in obtaining this predetermined backing off angle, which is ascribable, in practice, to the impossibility of ensuring an accurate and invariable positioning of the parts to be considered, to wit: the cutter tooth and the operative surface of the grinding wheel. Now, any small modification in the relative position of the grinding wheel with reference to the cutter corresponds to a large modification in the backing off angle. As a matter of fact, the backing off angle is obtained conventionally by positioning a tooth guide so as to obtain the desired position for the ridge of the cutter tooth with reference to the operative surface of the grinding wheel and to the axis of the cutter, the accuracy :of the backing oflf angle depending with an allowance within A of a millimeter on the position given to said tooth guide and the above-referred to relative positions should necessm'ly remain unmodified in spite of the wear of the grinding wheel. There are generally used for the sharpening of cutters, so-c-alled bushel-shaped grinding wheels which are constituted by a frusto-conical wall of a predetermined thickness, said grinding wheel operating through the edge of said wall which is slightly sloping with reference to the direction of progression of the cutter-carrying table. The backing oif angle is defined by setting first the tooth against an abutment at a predetermined height equal to the height of the axis of the cutter-carrying centers, which allows then defining the reference height of the tooth guide. At this moment, the backing oif angle of the cutter tooth is equal to zero, if, however, the horizontal generating line extending in contact with the operative surface of the grinding wheel lies in the horizontal plane passing through the axis of the grinding Wheel. This being done, the machine bed is caused to sink vertically together with the cutter by a predetermined amount depending on the diameter of the cutter to be sharpened and on the desired backing oif angle.

Whereas said method may theoretically lead to accurate results, in practice, it is very difficult, if not impossible, to execute the above-mentioned adjustment with a sufl'icient accuracy. As a matter of fact, it is hardly feasible to keep a tooth of the cutter in the horizontal plane passing through the center of the machine and the axis of the grinding wheel and at the same time to bring and to lock the tooth guide into said horizontal plane. It should also be remarked that the operative ridge of the tooth guide, the slope of which matches generally the helical slope of the cutter and which has a substantial breadth, should have the middle of the breadth of said ridge in registry with reference to the height of the centers and it is also necessary for said middle point to register with a horizontal generating line through which the grinding wheel engages the cutter. The last operation which consists in making the axis of the cutter sink by a 3,1 12,582 Patented Dec. 3, 1963 "ice predetermined value, does not show any special difiiculty. Obviously, the wear of the grinding wheel and each dismantling of the cutter modify the adjustments, so that it is necessary to begin these over again after each truing of the grinding wheel and for each further grinding operation.

My invention has for its object an improvement in cutter-grinding or sharpening machines, according to which improvement, the operative surface of the grinding wheel of the bushel type is constituted by a surface of revolution of which the generating line extending in a horizontal plane defined by the tooth guide, is constituted by a straight line, the position of which does not vary and which is parallel or substantially parallel with the axis of progression of the cutter-carrying table, the generating line of the lateral surface of the grinding wheel in the same horizontal plane being a straight line perpendicular to the axis of progression of the cutter-carrying table. The position of the tooth guide does not vary with reference to the generating lines of the operative surface and of the lateral surface of the grinding wheel, while the vertical axis of the tooth guide passes through a point lying between the right-hand and the left-hand ends of the horizontal breadth of the operative line of the grinding wheel engaging the cutter. In such a machine, the backing off angle is adjusted through a vertical shifting of the cutter-carrying table with reference to the stationary tooth guide.

The relative cooperating positionings referred to hereinabove are obtained through a truing of the three main surfaces of the grinding wheel as provided by the arrangements to be described hereinafter. These relative positionings vary whatever may be the wear of the grind-,

ing wheel; the breadth of the cutting ridge of the latter remains constant through a truing of its operative sur face, the grinding Wheel returns into the accurate position occupied by it before its truing and, lastly, the position of the tooth guide being defined once and for all with reference to the generating lines of the grinding wheel as described hereinabove, it is possible to obtain without any error the desired backing off angle for the cutter after a single adjustment: a vertical relative shifting between the cutter-carrying table and the grinding wheel, the axis of which moves in unison with the tooth guide, the value of which shifting may be read on a meter or on a scale with reference to a constant level such preferably as that of the horizontal sharpening plane defined on the grinding wheel by the location of the tooth guide.

The tooth guide is stationary and is suitably positioned on the machine with reference to the grinding Wheel in an interchangeable manner, so as to allow resorting to a tooth guide, of which the ridge has a slope equal to the helicalslope of the cutter to be sharpened and also with a View to changing said tooth guide when worn, the position defined by the different tooth guides remaining invariable.

The tooth guide may slope with reference to a. vertical line by an angle ranging between zero and twenty degrees, without its length being modified, this being obtained through a change of its support. Such an arrangement is provided so as to further the mounting of certain types of cutters.

In the case where the sharpening of helical cutters 'is provided with a positive control of the rotation of the cutter, which rotation is in direct relationship with the through the middle of the horizontal breadth of the reduced operative surface of the grinding wheel at the level of the selected horizontal sharpening plane.

If the selected sharpening plane is constituted by the horizontal plane passing through the axis of the grinding wheel, the operative surface of the grinding wheel and also the outer surface of the grinding wheel are constituted by frusto-conical surfaces having for their apex V a point of the axis of the grinding wheel.

If the selected sharpening plane is a horizontal plane which is shifted vertically above or underneath the horizontal plane passing through the axis of the grinding wheel, the operative surface of the grinding wheel is formed then as also its lateral surface by a section of a hyperboloid and their generating lines in the sharpening plane are constituted by straight lines, as in the preceding case.

In the case where the sharpening plane is vertically shifted with reference to the horizontal plane passingthrough the axis of the grinding wheel, the plane tangent to the operative surface of the grinding wheel is no longer vertical and it is necessary to take this in account for the calculation of the backing off angle.

It has appeared that, in order to provide in practice any desired grinding or sharpening, it is of particular itnerest to work in a plane which is vertically shifted with reference to the horizontal plane passing through the axis of the grinding wheel, which latter plane will be termed hereinafter the sharpening plane. In practice, if I resort, for instance, to a bushel-shaped grinding wheel having a diameter of 100 mm. and if a vertical shifting by 25 mm. is resorted to with a grinding wheel shaft forming an angle of with the perpendicular to the direction of progression of the table carrying the grinding wheel, the modifications in the backing off angle may be maintained within very restricted limits, which allows, for instance, obtaining 'a well-defined backing off angle with a modificationrvarying by :18, whatever may be the extent of wear of the grinding wheel.

Furthermore, depending on the cutters to be sharpened, it may be necessary to work with the axis of the grinding wheel sloping towards the right-hand side or towards the left-hand side, underneath or above the horizontal diametrical plane of the wheel. By reason of the symmetrical structure of a hyperboloid of revolution, these four positions may be obtained simply by reversing, when required, the slope of the axis of the grinding wheel with reference to the direction of progression of the cutter-carrying table. The head carrying the grinding wheel is consequently pivota-lly secured on its carriage, so as to be capable. of moving round a vertical axis, while the locking means allow holding it fast in at least the two above-mentioned positions. 7

My invention has for its object also the means and arrangements of the machine which ensure a correct truing of the grinding wheels. a

'One of said arrangements ensures the truing of the lateral surface of the grinding wheel. The shape of the outer surface of the latter is not modified by the wear of the grinding wheel and, consequently, this truing is performed once and for all when the grinding wheel is to be used for the first time and it may be executed as a previous step on a number of grinding wheels at a time. The truing means include a support secured to the cutter-carrying.

table, to the pedestal of the machine, to the casing of the machine head or to the carriage carrying the grinding Wheel and which is provided with a slideway directed in parallelism with the axis of progression of the carriage carrying the grinding wheel, that is to say perpendicular to the direction of progression of the cutter-carrying table; inside said slideway may slide, under the action of a suitable controlling system a diamond adapted to follow a straight line located in the sharpening plane at an unvarying distance from the vertical plane parallel with the direction of progression of said carriage and passing through the vertical axis of the tooth guide. According to an auxiliary feature of my invention, said slideway is;

pivotally secured round an axis perpendicular to the table lying at the same level as the sharpening plane, so as to allow the slideway to occupy the two horizontal positions symmetrical with reference to said axis, which ensure the truing of a grinding wheel with a slope towards the right-hand side or towards the left-hand side. According to a further auxiliary feature, the diamond may be urged away along a horizontal line perpendicular to its direction of progression, so as to allow executing roughening cuts, while an abutment defines its position along the final truing line; lastly, according to a still further auxiliary feature, when the arrangement is carried by the cuttercarrying table, there is provided a stop on the frame, which stop ensures the positioning of the slideway in either of its positions with reference to the truin g line.

The improved arrangement for truing the terminal surface and the edge of the inner surface of the grinding wheel is collapsible and is carried by a truing head adapted to assume a vertical movement, while its lower position is defined by an abutment which brings the truing diamond for the front surface into the sharpening plane or, in a more particular manner, into a horizontal plane arranged symmetrically of the sharpening plane with reference to the horizontal axial plane of the grinding wheel. The uial truing arrangement includes a slideway adapted to assume a longitudinal movement and carrying the diamond for truing the terminal surface of the grinding wheel and two vertical stub shafts arranged to either side of the path followed by said diamond and carrying each a lateral diamond for the truing of the edge of the inner surface and driven by a pinion cooperating with a rack provided on said slideway, the operative range of the last-mentioned diamonds adapted to true the edge of the inner surface being such that said diamond cuts the hyperboloid described by the diamond truing the front surface, while the horizontal breadth of the front surface of the grinding wheel in the sharpening plane is equal to a predetermined value equal in practice to about 1 mm. In order to further the execution of the machine, the diamonds truing the edge of the inner surface are vertically shifted with reference to the sharpening plane.

In order to ensure the truing of the grinding wheel without dismantling the tools which may be fitted on the bed of the machine, the spindle carrying the grinding wheel is fitted on a carriage adapted to move in a horizontal plane in a direction perpendicular to the axis of progression of the cutter-carrying table, while the tooth guide remains stationary;

In order to ensure the desired accuracy for the posi-- tioning of the grinding wheel, in contact with the tooth guide, after each truing of the' grinding wheel, the frame.

is provided with a stop for the carriage of the grinding wheel, which stop is adapted to receive a micrometric shifting along a line perpendicular to the direction of movement of the cutter-carrying table, said stop being rigid with a second collapsible stop lying with a spacing movements of the truing head and the collapsing of the stop are controlled by hydraulic means and control one another.

I will now describe my invention with further detail, reference being made to the accompanying drawings, wherein:

FIG. 1 is a horizontal axial sectional view of a grinding wheel adapted to operate in a horizontal plane passing through the axis of the grinding wheel.

FIG. 2 is an elevational view corresponding to a projection, on a plane parallel with the direction of progression of the cutter-carrying table, of the grinding wheel and of the tooth guide.

FIG. 3 is a lateral elevational view, corresponding to a projection on a plane perpendicular to the direction of movement of the cutter-carrying table, of the grinding wheel, of the tooth guide and of the cutter.

FIG. 4 is a horizontal sectional view passing through the axis of a hyperboloid-shaped grinding wheel adapted to operate underneath the horizontal plane passing through the axis of said grinding wheel.

FIG. 5 is a view, corresponding to FIG. 3, of the grinding wheel of the type illustrated in FIG. 4.

FIG. 6 is a general lateral elevational view of the machine for the sharpening of cutters, according to the invention.

FIG. 7 is a plan view, on a larger scale, of a carriage carrying the grinding wheel associated with the means for truing the lateral surface of the wheel when positioned for operation.

FIG. 8 is a sectional view, through line VIII-VIII of FIG. 7, of said wheel-truingmeans.

FIG. 9 is a sectional view of the same means through line IX-IX of FIG. 7.

FIG. 10 is a plan view thereof.

FIG. 11 is a lateral elevational partly sectional view of the machine head.

FIG. 12 is a view similar to FIG. 11, showing the said head during the truing of the front and inner surfaces of the grinding wheel.

FIG. 13 is a horizontal cross-section illustrating diagrammatically the means for truing the front and inner surfaces of the grinding wheel.

FIG. 14 is a diagrammatic vertical sectional view of the means illustrated in FIG. 13.

FIG. 15 is a partly sectional plan view thereof.

FIG. 16 is a diagrammatic view of the hydraulic control means.

FIG. 17 is a diagram of the interconnecting arrangement.

Turning to FIGS.'1 to 3, the grinding wheel is of the so-called bushel type, in the shape of a frusto-conical skirt, the apical angle of which, in the case illustrated, is equal to said grinding wheel being adapted to operate inthe horizontal plane passing through its axis. A generating line XX forms thus with the axis AA of the grinding wheel at angle of 15. The surface of'the grinding wheel is defined in accordance with the invention by three surfaces. The peripheral surface 2 which is perfectly frusto-conical, has an apical angle equal to 30 and the axis of the grinding wheel is horizontal and lies at 15 from the direction of progression xx of the carriage on which the grinding wheel is fitted, said axis of progression being, in its turn, perpendicular to the direction 00' of progression of the cutter-carrying table; the generating line of said surface in an axial horizontal plane is thus parallel with the axis of progression of the grinding wheel and it retains said direction during the adjustments of the grinding wheel required by the diameter of the cutter or the wear of the grinding wheel. The terminal surface 3 or operative surface has all the radial lines drawn thereon perpendicular to the peripheral surface 2 and forms a frusto-conical surface, the'apex of which is shown at S on the axis AA, the apical angle of said surface forming the supplement of the apical angle of the outer surface 2. The inner surface 4 of the grinding wheel is a true frusto-conical surface, the part played by which consists in ensuring a constant value for the breadth of the surface 3. a

FIG. 2 shows the interest of a grinding wheel executed in the manner described: the horizontal generating line S0 of the surface '3 is parallel with the direction of movement of the cutter-carrying table and along said horizontal generating line SO, the tangents to the directing lines of said frusto-conical surface 3 are all directed vertically and lie in a common plane. The grinding wheel acts thus in practice after the manner of a flat disc, the mean radius of which is large with reference to the breadth of the frusto-conical surface 3. The wear of the wheel is distributed theoretically in a uniform manner throughout the surface 3. In practice, the truing of the surface 3 is executed after each sharpening operation.

In order to ensure a correct positioning of the tooth and to define the horizontal line SO, I resort to a tooth guide 5 carried by the head 6 of the machine through the agency of a centering stud 7 and removable securing means constituted, for instance, by a screw 8, so that said tooth guide 5, while remaining removable, may never theless have a point 9 of its edge, which is defined by its medial vertical axis, lying in the horizontal axial plane of the grinding wheel on the perpendicular to the direction of progression of the cutter-carrying table passing substantially through the middle of SO, the generating line of the surface 3. The lower edge ltl of the tooth guide is either horizontal, or slopes at an angle equal to the pitch of the helical tooth in the cutter to be sharpened.

In the case of some cutters, it is impossible to operate in the diametrical plane of the grinding wheel and it is necessary to resort to the point T outside said plane (FIG. 2). it is apparent that at such a point, the perpendicula to the operative edge of the grinding wheel is no longer a horizontal such as TH, but a straight line TP and the wear of the grinding wheel leads to a modification in the radius of the circle forming the envelope of the ridges and this modification may be substantial. Furthermore, the location of the point T varies with the wear of the grinding wheel and when its level underneath the horizontal axial plane of the grinding wheel is constant, that is when the tooth guide has a constant height, it is shifted laterally.

In order to remove the above drawbacks, the conventional grinding wheel is rectified so as to be given a special shape illustrated in FIGS. 4 and 5, the outer surface 11 of which is a hyperooloid of revolution, that is to say a surface of which the generating line leading to he tooth guide is horizontal and perpendicular to the direction of progression of the cutter-carrying table; the lateral surface 12 is also a hypenboloid of revolution generated by a horizontal line perpendicular to the straight line referred to hereinabove and rotating round. the axis of the grinding wheel, the generating lines of said surface in horizontal planes being h-yperbolas as at 12'. The inner surface 13 is also constituted by a hyperboloid of revolution. in FIG. 4, the lines 14, 15, 16 drawn in interrupted lines illustrate the intersections of the edges of the surfaces 11 and 13 respectively by a horizontal plane. theoretically on the ridge of a tooth along a line parallel with the axis of the cutter or, more accurately, along a line parallel with the direction of progression of the cutter-carrying table, but it is apparent, on the one hand, that the tangent 16 to the outer circle defining the surface 12 of the grinding wheel, slopes less withreference to a vertical line than the tangent 17 to the inner circle and, on the other hand, that said tangent which enters'the position 13' when the line 15 reaches the position 18, has a tendency to slope more and more towards a horizontal plane when the grind-ing wheel becomes worn and its diameter is thus reduced. It is possible to calculate the This type of grinding wheel operates 7 modifications of the angles between the tangents i6, 17 (or l8), and a vertical line.

Assuming the grinding wheel has originally a rad-ins of cm., that is the distance of the crossing point between the straight lines 14 and 15 with reference to the axis of the grinding wheel, the inner circle having a radius that is the distance between the crossing point of the straight lines 15 and 16 and said axis is equal to 4.9 cm., while the tooth guide lies at 25 mm. underneath the horizontal plane passing through the axis of the grinding wheel, ofwhich the axis forms an angle of with the vertical plane passing through the straight line 14, there is obtained, q: being the angle of thestraight line 16 andwith a vertical line:

(p being the angle between the straight line 17 and a vertical line, there is obtained:

If the grinding wheel is worn by 2 cm., whereby the radius of its outer surface becomes equal to 4.65 cm. which corresponds to a position as illustrated at 18, becomes equal to for which:

It is thus apparent that in such a case, it is of advantage to reduce to a maximum the breadth of the operative surface, so as to reduce the difference between the angles (p and which is obtained readily by truing the inner surface 13 of the grinding wheel, while I may not take into account the modifications in the outer diameter of the grinding wheel, the actual backing off angle varying, within the allowedlimits of wear of the grinding wheel, only by 38 minutes between a new grinding Wheel and the grinding wheel when worn to the allowed extent. It is however possible to take into account such modifications.

The machine illustrated in FIGS. 6 to includes a frame 21 form-ing a pedestal. Said pedestal carries in a conventional manner, through the agency of dove tailed or the like slideways, the bed 22 adapted to be subjected, under the control of the handwheel 23, to a shifting ina direction perpendicular to the direction of progression of the center-carrying table 24. The shiting of the center-carrying table 24 carried by a dovetailed slideway 25 or the like over the bed 22, is controlled, in a conventional manner, by a handwheel 26. Thecutters 27 are fitted between the centers 28 and the rotation of'a cutter may be controlled by hand, or else, the cutter may be driven into rotation in a conventional manner, tinder the control of the shifting of the table by a sinus bar or a harness, chiefly in the case of the cutters having a high pitch. 7

Furthermore, in the frame 21, there is fitted, in a conventional manner, a column 31 carrying the sharpening head 32 of the machine so that said column may slide vertically under the action of a control handwheel 29,

'. a micrometric positioning being obtained by a meter 39.

Said sharpening head includes a pedestal 33 provided with two slideways 34 inside which may slide the carriage 35 carrying the grinding wheel under the action of a control system such as a nut 36 associated with a worm 37 controlled by a hand-wheel 38 (FIG. 11). On said carriage 35 is revolvably mounted round a vertical axis the plate 39* carrying the casing 46 for the shaft driving the grinding wheel and to which is secured the driving motor 41. The plate 39 is provided along its rear edge 42 extending coaxially with reference to the axis of rotation of said plate with three notches 43 adapted to cooperate with a locking pin 44 fitted on the carriage 355. The three notches 43 are arranged in a manner such that the locking pin-44 may ensure selectively for the shaft 46 carrying the grinding wheel, that is for the axis of the grinding wheel 57, a first position parallel with the direction of progression of the carriage 35 and two further positions angularly shifted with reference to the direction of progression of the carriage 35, by symmetrical values equal to 10 on either side of said direction, for instance.

The pedestal 33 of the head carries furthermore a stop 47 adapted to slide along the direction of progression of the carriage 35 under the action of a micrometric control system 48, said stop cooperating with the front edge 49 of the carriage. The body of said stop 47 carries furthermore a second collapsible stop 50 spaced from the former stop 47 by a distance to be defined hereinafter and which is equal to the horizontal spacing between the sharpening line and the truing line.

The sharpening line is defined by the ridge of the tooth guide 51, which latter may be changed, as disclosed hereinabove, in accordance with the cutters to be sharpened, while its medial vertical axis passes through the middle of the horizontal breadth of the operative line of the grinding wheel. Said guide ridge is located at a distance selected, in this example, at 25 mm. underneath the horizontal plane passing through the axis of the grinding wheel. The tooth guide is carried by a head 52 rigid with the casing 46 of the grinding head. The casing 46 carries furthermore a wheel-truing head 53 adapted to move vertically inside the casing under the action, for instance, of manually operated means, including a threaded rod 54 and a handwheel 55; said head 53 is provided furthermore with cutting diamonds for the front and inner surfaces of the wheel, as described with further detail hereinafter. The wheel-truing line defining, with the reference mark on the tooth guide, the distance between the stationary stop 47 and the collapsible stop 50, forms a straight line perpendicular to the direction of progression of the carriage 35 for the grinding wheel, as described by the diamond 77 truing the front surface of the grinding wheel.

According to the invention, the grinding wheel should be trued in a manner such that, in the horizontal sharpening plane corresponding to apredetermined point of the ridge on the tooth guide, which plane is selected, in the case considered, at 25 mm. underneath the axis of the grinding wheel 57, the cross-section of the grinding wheel includes a rectilinear lateral surface which is perpendicular to the direction of progression of the center-carrying table 24, that is which is parallel with the direction of progression of the carriage 35, and a rectilinear front surface perpendicular to the former surface, to wit: a front surface of a reduced breadth; this results in that the lateral and front surfaces of the grinding wheel are constituted by hyperboloids of revolution.

The truing of the lateral surface of the grinding wheel previously to 'its operation is performed by the arrangement illustrated in detail in FIGS. 8 to 10. As illustrated in FIG. 7, the arrangement is fitted on the center-carrying Said shaft has its axis extending above the surface of the table at a level underneath the axis of the centers by an amount equal to the vertical spacing of the sharpening plane with reference to the axis of the grinding wheel, to wit, in the present case, mm., whereby, when the head of the grinding wheel engages its abutment for its lowermost position and the axis of the grinding wheel lies on the same level as the axis of the centers, the axis of said shaft 64 lies in the truing plane of the grinding wheel. To said shaft 64 is secured revolvably, through two lugs 65, a slideway body 66 provided with a surface 67 adapted to engage through an angular shifting of the shaft 64 either of the surfaces 62 and -to be held against the latter by a bolt which is not illustrated and which is screwed into the body 61 and engages either of the notches 68 (FIG. 9). The slideway body encloses a rack 69 driven by a controlling handwheel 70, which rack carries the number 71 guiding the diamond carrier. The member '71 passes through a port 72 in the slideway body, so as to project beyond the surface of the latter facing the shaft 64, the axis of the member 71 guiding the diamond carrier lying in the horizontal plane of the axis of the shaft 64. The diamond carrier 73 is adapted to move axially inside the body 71, as provided by the screwing or unscrewing by means of a micrometric adjusting knob 74, but its extreme position towards the axis of the shaft 6 is limited by a stop, whereby the diamond 75 is aligned with the generating line corresponding to the lateral surface of the grinding wheel in the selected sharpening plane.

A stop 76 provided on the pedestal 33 of the head cooperates with the slideway body 66, so as to define selectively one of the two positions for wheel-truing, the second position being illustrated in dot-and-dash lines in FIG. 8, for the cutting of grinding wheels sloping towards the left-hand side or towards the right-hand side respectively. The wheel-truing arrangement for the lateral surface of the grinding wheel may also be provided with a base forming a bracket secured at a predetermined point to the pedestal 33 carrying the head.

In order to proceed with the truing of a rough grinding wheel into the shape of a frusto-conical bushel, which wheel has been previously secured to the shaft which is to carry it, the wheel-truing means are fitted either on the pedestal 33, in which case said means are subjected to a preliminary adjustment or else, on the table 24, in which case the head carrying the grinding wheel is brought vertically into abutment in its lower-most position, the slideway body being urged into contact with the stop 76. The grinding wheel being driven into rotation, the knob 74 is actuated so as to move the diamond gradually towards the wheel by making it progress along the lateral surface of the grinding wheel through the agency of the handwheel 70. When the diamond carrier arrives against its stop, the lateral cutting of the grinding wheel is finished.

The wheel-truing of the front surface and of the edge of the inner surface of the wheel is performed periodically by means of the truing head 53; the latter carries at its lower end (FIG. 13) the diamond 77 facing the grinding wheel and rigid with a rack 78 which is subjected, by a control system acting on the studs 9, to a transverse reciprocating movement in a direction perpendicular to the progression of the carriage for the grinding wheel, whereby the terminal surface of the wheel is trued. The truing of the inner edge of the grinding wheel with a view to obtaining a constant breadth for the sharpening line, is performed through either of the diamonds 80 according as to whether the grinding wheel slopes towards the left or towards the right-hand side, each diamond 80 being driven along an arcuate path by a pinion '81 meshing with the rack 78 and their path cuts the path of the diamond 77 at a distance from the lateral trued surface such that the operative surface of the grinding wheel may have a predetermined horizontal breadth of about 1 mm. in the sharpening plane. In practice and in order to ensure the desired release for the diamonds, the assembly is that illustrated in FIGS. 14 and 15. The truing of the front surface is performed by resorting to the symmetrical conditions at a predetermined height above the plane passing through the axis of the grinding wheel which is equal to the vertical shifting h of the. sharpening plane, to wit: 25 mm. in the example considered. The diamonds act in a plane which is shifted further upwardly, which allows giving them a larger spacing, the front surface of the grinding wheel receding in said plane sideways and" rearwardly. The carrier 82 for the diamond 77 is secured inside the body 83 of a slider carrying the rack 78 meshing with the two small pinions 81, the spindle 84 of each of which is bored transversely, in its upper section, so as to be engaged by the diamond carrier 85 for the corresponding diamond 80, which carrier is held fast by the tip of a threaded pin 86 screwed into an axial tapping of the spindle 84. A rockable control lever 87 cooperates with the studs 79 to ensure the drive of the whole system.

For the truing of the front and inner surfaces, the carriage 35 for the grinding wheel is drawn rearwardly, the truing head 53 is caused to sink into its operative position, the collapsible stop 50 is set in position, the carriage 35 is shifted to obtain engagement with the diamond 77 and the truing head is operated by the lever 87, while the depth of truing is adjusted through the adjusting knob 48. When the truing is at an end, it is necessary to make the carriage 35 recede, to raise the truing head 53, to make the stop 5% collapse and to return the carriage 35 into abutment against the stop 47 so as to obtain a sharpening line in an unvaryingposition, whatever may be the extent of wear of the grinding wheel 57.

I have described, hereinabove, a sharpening machine wherein the control systems are operated manually, but it can be executed as well with hydraulic control systems, as illustrated in FIG. 16. There is substituted for the nut and screw control system of the carriage 35 carrying the wheel and of the truing head 53, double acting hydraulic jacks 87 and 88 controlled by the corresponding electromagnetically actuated slide valves 89 and 90.

The collapsible stop 50 is controlled by a single acting jack 91 controlled by an electromagnetically controlled distributing valve 92. The system is fed by a motordriven pump 93 sucking oil out of a vat 94 associated with feed pipes provided with non-return valves 95 and with return pipes.

The electromagnetic control systems are operatively interconnected in any desired manner, for instance through pressure-controlled switches or through end-ofstroke switches so as to execute the cycle illustrated in FEG. 17, wherein A corresponds to the carriage for the wheel, B to the truing head and C to the collapsible stop. The carriage 35 abutting against the stop 47 and the truing head 53 being in its raised position with the stop 59 in its collapsed position, it is suflicient to depress the knob at controlling the truning operation so that the circuit is closed and brings the slide valve 89 into the position for which the carriage 35 is urged back by the jack 87. At the end of the stroke, the pressure closes the pressure-controlled switch mAl which operates the relay Rdl which, in its turn, switches off the feed onto the control system for the slide valve the latter sends the oil under pressure into the upper chamber of the jack 88, which makes the head 53 sink. 'At the end of the stroke, the pressure-operated gauge mBl switches the feed through the relay Rd2 into the valve 92, which feeds the oil under pressure into the jack 91, which sets the stop 5! in position; at the end of the stroke, the pressure-operated switch mCl sends the oil under pressure into the'slide valve 89, so as to return through the jack 87 the carriage 35 against the stop 50. The arrangement is then set in the position required for truing.

When the tnling is finished, the knob a corresponding to the sharpening, is depressed. A current passes through the normally non-energized relay Ral so as to reverse the position of the slide'valve 89, which urges backvthrough the double acting jack 87 the carriage for the grinding wheel. When said carriage reaches its stop, the pressure-operated switch mAl closes and sends the oil through the inoperative relay RaZ into the control means for the slide valve 99, which feeds the oil under pressure into the lower chamber of the jack 88 and raises the truing head 53. At the end of the stroke, the pressure-operated switch mRZ closes and feeds Ra2, which sets the slide valve 92 into the position corresponding to exhaust. The stop 50 collapses and closes at the end of the stroke the switch 001, through the relay R113, changes the fed of the slide valve 89 and returns the carriage 15 forwardly through operation of the jack 87 until it abuts against the stop 47.

it is possible to use the pressure-controlled switch mAZ carried inside the rear chamber of the jack 87 for the control of the operation of the knobs d and a, so as to associate said operation with the abutment of the carriage 35'against one of the stops, with a view to cutting out any erroneous sequence of operations.

The embodiments described hereinabove, by Way of example, may obviously be modified in any suitable manner, within the scope of the accompanying claims.

What I claim is:

a 1. A cutter-sharpening machine comprising a pedestal, a table carrier adapted to reciprocate in a predetermined direction on the pedestal, a cutter carrying table adapted to move on said table carrier in a direction perpendicular to said predetermined direction, a sharpening head, a column carrying said head and vertically shiftable with reference to the pedestal, a grinding means carrying table carried by said sharpening head and reciprocable in an horizontal plane in a direction towards and from the cutter carrying table, a bushelshaped grinding wheel revolvably carried by said grinding means carrying table, said bushel-shaped grinding wheel having a front operative surface with a rectilinear generating line and a lateral surface with a rectilinear generating line, power means driving said grinding wheel, a tooth guide carried by the sharpening head and cornprising a free edge the center of which is in a fixed position relative to the sharpening head, intended to cooperate with the tooth of the cutter to be sharpened and with the front operative surface 'of the grinding wheel in its position towards the cutter carrying table, the tooth guide free edge defining on the front operative surface of the grinding wheel an operative line of a reduced breadth the center of which coincides with an horizontal plane comprising a rectiliner generating line of the front operative surface and a rectilinear generating lineof the lateral surface of the grinding wheel, said rectilinear generating line of the front operative surface being in substantial parallelism with the direction of movement of the cutter carrying table and said rectilinear generating line of the lateral surface being in substantial parallelism with the direction of movement of the grinding means carrying table.

2. A cutter-sharpening machine comprising a' pedestal, a table carrier adapted to reciprocate in a predetermined direction on the pedestal, a cutter carryingtable adapted to move on said table carrier in a direction perpendicular to said predetermined direction, a sharpening head, a column carrying said head and vertically shiftable with reference to the pedestal, a grinding means carrying table carried by said sharpening head and reciprocable in an horizontal plane in a direction towards and from the cutter carrying table,,a bushel-shaped grinding Wheel revolvably carried by said grinding means carrying table, said bushelshaped grinding wheel having a front operative surface with a rectilinear generating line and a lateral surface with a rectilinear generating line, power means driving said grinding wheel, an interchangeable tooth guide carried by the sharpening head and comprising a free edge the center of which is in a fixed position relative to the sharpening head, intended to cooperate with the tooth of the cutter to be sharpened and with the front operative surface of the grinding wheel in its position towards the cutter carrying table, the tooth guide free edge forming with the vertical an angle equal to the pitch of the cutter teeth to be sharpened and defining on the front operative surface of the grinding wheel an operative line of a reduced breadth the center of which coincides with an horizontal plane comprising a rectilinear generating line of the front operative surface and a rectilinear generating line of the lateral surface of the grinding wheel, said rectilinear generating line of the front operative surface being in substantial parallelism with the direction of movement of the cutter carrying table and said rectilinear generating line of the lateral surface being in substantial parallelism with the direction of movement of the grinding means carrying table.

3. A cutter-sharpening machine comprising a pedestal, a table carrier adapted to reciprocate in a predetermined direction on the pedestal, a cutter carrying table adapted to move on said table carrier in a direction perpendicular to said predetermined direction, a'sharpening head, a column carrying said head and vertically shiftable with reference to the pedestal, a grinding means carrying table carried by said sharpening head and reciprocable in an horizontal plane in a direction towards and from the cutter carrying table, a bushel-shaped grinding wheel revolvably carried by said grinding means carrying table, said bushelshaped grinding wheel having frustro conical front and lateral surfaces of which the rectilinear generating lines are perpendicular, a tooth guide carried by the sharpening head and comprising a free edge the center of which is in a fixed position relative to the sharpening head, intended to cooperate with the tooth of thelcutter to be sharpened and with the front operative surface of the grinding wheel in its position towards the cutter carrying table, the tooth guide free edge defining on the front operative surface of the grinding wheel an operative line of a reduced breadth the center of which is in the horizontal plane comprising the grinding wheel axis and the rectilinear generating line of the front operative surface passing through said center being in substantial parallelism with the direction of movement of the cutter carrying table.

4. A cutter-sharpening machine comprising a pedestal, a table carrier adapted to reciprocate in a predetermined direction on the pedestal, a cutter carrying table adapted to move on said table carrier in a direction perpendicular to said predetermined direction, a sharpening head, a column carrying said head and vertically shiftable with reference to the pedestal, a grinding means carrying table carried by said sharpening head and reciprocable in an horizontal plane in a direction towards and from the cutter carrying table, said bushel-shaped grinding wheel having front and lateral surfaces constituted by section of hyperboloids, a tooth guide carried by the sharpening head and comprising a free edge the center of which is in a fixed position relative to the sharpening head, intended to coop erate with the front operative surface of the grinding wheel in its position towards the cutter carrying table, the tooth guide free edge defining on the front operative surface of the grinding wheel an operative line'of a reduced breadth the center of which is in the horizontal plane comprising rectilinear generating lines of the front and lateral surfaces both said rectilineargenerating lines being perpendicular and the rectilinear generating line of the front operative surface passing through said center being in substantial parallelism with the direction of movement of the cutter carrying table.

5. A cutter-sharpening machine comprising a pedestal,

a table carrier adapted to reciprocate in a predetermined direction on the pedestal, a cutter carrying table adapted to move on said table carrier in a direction perpendicular to said predetermined direction, a sharpening head, a colunm carrying said head and vertically shiftable with reference to the pedestal, a grinding means carrying table carried by said sharpening head and reciprocable in an horizontal plane in a direction towards and from the cutter carrying table, a spindle revolvably carried by said grinding means carryin table and adapted to be angularly shifted round a vertical axis, means for locking said spindle at least in two angular positions symmetrical with reference to the direction of movement of the grinding means carrying table, means driving said spindle into rotation, a bushel-shaped grinding wheel rigid with said spindle said bushel-shaped grinding wheel having a front operative surface with a rectilinear generating line and a lateral surface with a rectilinear genera-ting line, a tooth guide carried by the sharpening head and comprising a free edge the center of which is in a fixed posit-ion relative to the sharpening head, intended to cooperate with the tooth of the cutter to be sharpened and with the front operative surface of the grinding wheel in its position towards the cutter carrying table, the tooth guide free edge defining on the front operative surface of the grinding wheel an operative line of a reduced breadth the center of which coincides with an horizontal plane comprising a rectilinear generating line of the front operative surface and a rectilinear generating line of the lateral surface of the grinding wheel, said rectilinear generating line of the front operative surface being in substantial parallelism with the direction of movement of the cutter carrying table and said rectilinear generating line of the lateral surface being in substantial parallelism with the direction of movement of the grinding means carrying table.

6. A cutter-sharpening machine comprising a pedestal, a table carrier adapted to reciprocate in a predetermined direction on the pedestal, a cutter carrying table adapted to move on said table carrier in a direction perpendicular to said predetermined direction, a sharpening head, a column carrying said head and vertically shiftable with with reference to the pedestal, a grinding means carrying table carried by said sharpening head and reciprocable in an horizontal plane in a direction towards and from the cutter carrying table, a bushel-shaped grinding wheel revolvably carried by said grinding means carrying table, said bushel-shaped grinding wheel having a front operative surface with a rectilinear generating line and a lateral surface with a rectilinear generating line, power means driving said grinding wheel, a tooth guide carried by the sharpening head and comprising a free edge the center of which is in a fixed position relative to the sharpening head, intended to cooperate with the tooth of the cutter to be sharpened and with the front operative surface of the grinding wheel in its position towards the cutter carrying table, the tooth guide free edge defining on the front operative surface of the grinding wheel an operative line of a reduced breadth the center of which coincides with an horizontal plane comprising a rectilinear generating line of the front operative surface and a rectilinear generating line of the lateral surface of the grinding wheel, said rectilinear generating line of the front operative surface being in substantial parallelism with the direction of movement of the qutifil carrying table and said rectilinear generating line of the lateral surface being in substantial parallelism with the direction of movement of the grinding means carrying table, and a truing system for the lateral surface of the grinding Wheel including a slideway extending perpendicularly to the direction of movement of the cutter-carrying table, a slider adapted to move in said slideway, a diamond rigid with said slider adapted to true the lateral surface of the grinding wheel in the horizontal plane passing through the center of the operative line of a reduced breadth along a straight line extending outside and at a short distance from said center, a truing head carried by the sharpening head and adapted to move vertically with reference to the latter, a further diamond carried by the truing head and adapted to assume a horizontal rectilinear movement along a line substantially parallel with the direction of movement of the cutter-carrying table, and at least one auxiliary diamond adapted to move along a circular path and to true the inner edge of the grinding wheel thereby to maintain a reduced breadth for the front operative surface of the grinding wheel.

7. A cutter-sharpening machine comprising a pedestal, a table carrier adapted to reciprocate in a predetermined direction on the pedestal, a cutter carrying table adapted to move on said table carrier in a direction perpendicular to said predetermined direction, a sharpening head, a column carrying said head and vertically shiftable with reference to the pedestal, a grinding means carrying table carried by said sharpening head and reciprocable in an horizontal plane in a direction towards and from the cutter carrying table, a bushel-shaped grinding wheel revolvably carried by said grinding means carrying table, said bushel-shaped grinding wheel having a front operative surface with a rectilinear generating line and a lateral surface with a rectilinear generating line, power means driving said grinding wheel, a tooth guide carried by the sharpening head and comprising a free edge the center of which is in a fixed position relative to the sharpening head, intended to cooperate with the tooth of the cutter to be sharpened and with the front operative surface of the grinding wheel in its position towards the cutter carrying table, the tooth guide free edge defining on the front operative surface of the grinding wheel an operative line of a reduced breadth the center of which coincides with an horizontal plane comprising a rectilinear generating line of the front operative surface and a rectilinear generating line of the lateral surface of the grinding wheel, said rectilinear generating line of the front operative surface being in substantial parallelism with the direction of movement of the cutter carrying table and said rectilinear generating line of the lateral surface being in substantial parallelism with the direction of movement of the grinding means carrying table and a truing systerm for the lateral surface of the grinding wheel including a slideway extending perpendicularly to the direction of movement of the cutter-carrying table, a slider adapted to move in said slideway, a diamond rigid with said slider and adapted to true the lateral surface of the grinding wheel in the horizontal plane passing through the center of the operative line of a reduced breadth along a straight line extending outside and at a short distance from the axis of the said center, a truing head carried by the sharpening head and adapted to move vertically with reference to the latter, a further diamond carried by the truing head and adapted to assume a horizontal rectilinear movement along a line substantially parallel with the direction of movement of the cutter-carrying table, a stop defining the lowermost position of the vertical movement of the truing head to position the diamond carried by the latter in a horizontal plane symmetrical of the horiz'ontal plane passing through the center of the operative line of a reduced breadth with reference to the horizontal axial plane of the grinding wheel, and at least one auxiliary diamond adapted to move along a path vertically shifted with reference to the operative path of last-mentioned diamond.

8. A cutter-sharpening machine comprising a pedestal, a table carrier adapted to reciprocate in a predetermined direction on the pedestal, a cutter carrying table adapted to move on said table carrier in a direction perpendicular to said predetermined direction, a sharpening head, a column carrying said head and vertically shiftable with reference to the pedestal, a grinding means carrying table carried by said sharpening head and reciprocable in an horizontal plane in a direction towards and from the cutter carrying table, a bushel-shaped grinding wheel revolvably carried by said grinding means carrying table, said bushel-shaped grinding wheel having a front operative surface with a rectilinear generating line and a lateral surface with a rectilinear generating line, power means driving said grinding wheel, a tooth guide carried by the sharpening head and comprising a free edge the center of which is in a fixed position relative to the sharpening head, intended to cooperate with the tooth of the cutter to be sharpened and with the front operative surface of the grinding wheel in its position towards the cutter carrying table, the tooth guide free edge defining on the front operative surface of the grinding wheel an operative line of a reduced breadth the center of which coincides with an horizontal plane comprising a rectilinear generating line of the front operative'surface and a rectilinear generating line of the lateral surface of the grinding wheel, said rectilinear generating line of the front operative surface being in substantial parallelism with the direction of movement of the cutter carrying table and said rectilinear generating line of the lateral surface being in substantial parallelism with the direction of movement of the grinding means carrying. table and a truing system for the lateral surface of the grinding wheel including a slideway extending perpendicularly to the direction of movement of the cutter-carrying table, a slider adapted to rim-l 'move in said slideway, a diamond rigid with said slider and adapted to true the lateral surface of the grinding wheel in the horizontal plane passing through the center of the operative line of a reduced breadth along a straight line extending outside and at a short distance from the said center, a truing head carried by the sharpening head and adapted to move vertically with reference to the latter, a further diamond carried by the truing head and adapted to assume a horizontal rectilinear movement along a line substantially parallel with the direction of movement of the cutter-carrying table, a first stop carried by the sharpening head, cooperating with the grinding means carrying table and adapted to assume a micrometric movement in the direction of movement of said grinding means carrying table, a collapsible stop carried by the first stop, also cooperating with the grinding means carrying table, the distance between the first and the collapsible stop being equal to the distance along a horizontal line parallel with the direction of movement of the grinding means carrying table, between the edge of the tooth guide and the path followed by the diamond on the truing head and an auxiliary diamond adapted to move along a circular path and to true the inner edge of the grinding wheel thereby to maintain a reduced breadth for the front operative surface of the grinding wheel.

9. A cutter-sharpening machine comprising a pedestal, a table carrier adapted to reciprocate in a predetermined direction on the pedestal, a cutter carrying table adapted to move on said table carrier in a direction perpendicular to said predetermined direction, a sharpening head, a column carrying saidhead and vertically shiftable with reference to the pedestal, a grinding means carrying table carried by said sharpening head and reciprocable in an horizontal plane in a direction towards and from the cutter carrying table, a double acting hydraulic jack controlling the movements of said grinding means carrying table, atspindle revolvably carried by said grinding means carrying table, means driving said spindle into rotation, a bushel-shaped grinding wheel rigid with said spindle, a

16 tooth guide carried by the sharpening head and com prising a free edge the center of which is in a fixed position relative to the sharpening head, intended to cooperate with the tooth of the cutter to be sharpened and with the front operative surface of the grinding wheel in its position towards the cutter carrying table, the tooth guide free edge defining on the front operative surface of the grinding wheel an operative line of a reduced breadth the center of which coincides with an horizontal plane comprising a rectilinear generating line of the front operative surface and a rectilinear generating line of the lateral surface of the grinding wheel, said rectilinear generating line of the front operative surface being in substantial parallelism with the direction of movement of the cutter carrying table and said recilinear generating line of the lateral surface being in substantial parallelism with the direction of movement of the grinding means carrying table and atruing system for the lateral surface of the grinding wheel including a slideway extending perpendicularly to the direction of movement of the cutter carrying table, a slider adapted to move in'said slideway, a diamond rigid with said slider and adapted to true the lateral surface of the grinding wheel in the horizontal plane passing through the center of the operative line of a a reduced breadth along a straight line extending outside and at a short distance from the said center, a truing head, a further vertical double-acting jack carried by the sharpening head and including a piston carrying the truing head, a further diamond carried by said truing head and adapted to move along a horizontal straight line substantially parallel to the direction of movement of the cutter carrying table, means limiting the downward movement of last-mentioned jack to position the diamond carried by the latter in a horizontal plane symmetrical of the horizontal plane passing through the center of the operative line of a reduced breadth with reference tothe horizontal axial plane of the grinding wheel, at least one auxiliary diamond, adapted to move along a circular path and to true the inner edge of the grinding wheel thereby to maintain a reduced breadth for the front operative surface of the grinding wheel, a first stop carried by the sharpening head, cooperating with the grinding means carrying table References Cited in the file of this patent UNITED STATES PATENTS 2,429,250 Wiken et al Oct. 21, 1947 2,821,817 Zalewski Feb. 4, 1958 2,958,988 Crosby Nov. 8, 1960 PGREIGN PATENTS 262,538 Germany Sept. 27, 1912 

1. A CUTTER-SHARPENING MACHINE COMPRISING A PEDESTAL, A TABLE CARRIER ADAPTED TO RECIPROCATE IN A PREDETERMINED DIRECTION ON THE PEDESTAL, A CUTTER CARRYING TABLE ADAPTED TO MOVE ON SAID TABLE CARRIER IN A DIRECTION PERPENDICULAR TO SAID PREDETERMINED DIRECTION, A SHARPENING HEAD, A COLUMN CARRYING SAID HEAD AND VERTICALLY SHIFTABLE WITH REFERENCE TO THE PEDESTAL, A GRINDING MEANS CARRYING TABLE CARRIED BY SAID SHARPENING HEAD AND RECIPROCABLE IN AN HORIZONTAL PLANE IN A DIRECTION TOWARDS AND FROM THE CUTTER CARRYING TABLE, A BUSHELSHAPED GRINDING WHEEL REVOLVABLY CARRIED BY SAID GRINDING MEANS CARRYING TABLE, SAID BUSHEL-SHAPED GRINDING WHEEL HAVING A FRONT OPERATIVE SURFACE WITH A RECTILINEAR GENERATING LINE AND A LATERAL SURFACE WITH A RECTILINEAR GENERATING LINE, POWER MEANS DRIVING SAID GRINDING WHEEL, A TOOTH GUIDE CARRIED BY THE SHARPENING HEAD AND COMPRISING A FREE EDGE THE CENTER OF WHICH IS IN A FIXED POSITION RELATIVE TO THE SHARPENING HEAD, INTENDED TO COOPERATE WITH THE TOOTH OF THE CUTTER TO BE SHARPENED AND WITH THE FRONT OPERATIVE SURFACE OF THE GRINDING WHEEL IN ITS POSITION TOWARDS THE CUTTER CARRYING TABLE, THE TOOTH GUIDE FREE EDGE DEFINING ON THE FRONT OPERATIVE SURFACE OF THE GRINDING WHEEL AN OPERATIVE LINE OF A REDUCED BREADTH THE CENTER OF WHICH COINCIDES WITH AN HORIZONTAL PLANE COMPRISING A RECTILINEAR GENERATING LINE OF THE FRONT OPERATIVE SURFACE AND A RECTILINEAR GENERATING LINE OF THE LATERAL SURFACE OF THE GRINDING WHEEL, SAID RECTILINEAR GENERATING LINE OF THE FRONT OPERATIVE SURFACE BEING IN SUBSTANTIAL PARALLELISM WITH THE DIRECTION OF MOVEMENT OF THE CUTTER CARRYING TABLE AND SAID RECTILINEAR GENERATING LINE OF THE LATERAL SURFACE BEING IN SUBSTANTIAL PARALLELISM WITH THE DIRECTION OF MOVEMENT OF THE GRINDING MEANS CARRYING TABLE. 